Eliminate a frameback navigation initialization race (#518)
Eliminate a frameback navigation initialization race (#518)

During the first frameback navigation forward with `reuseFrame` set, if the
client controller within the frame completes before the frame's load event
fires we were previously failing to wire up our listener to handle subsequent
navigations.
lidawang/react-server,doug-wade/react-server,doug-wade/react-server,davidalber/react-server,redfin/react-server,szhou8813/react-server,szhou8813/react-server,davidalber/react-server,lidawang/react-server,emecell/react-server,emecell/react-server,redfin/react-server